This application is related to the application for a Floatless Carburetor by Thomas G. Guntly et al and assigned to a common assignee, filed on even dated herewith, Ser. No. 07/590,014.
This invention relates generally to manually compressible priming bulb assemblies for supplying a priming charge of fuel to a carburetor for internal combustion engines, and more particularly to apparatus for sealing and retaining the bulb in the carburetor.
Small internal combustion engines, such as those used in snow blowers, lawn mowers and the like generally require fuel mixture enrichment when starting, particularly when cold. For example, in cold weather the cranking resistance increases due to weather sensitivity of such things as oil viscosity and the like, which can slow down the cranking speed of the engine during starting. This reduces the velocity and fuel intake and, in addition due to the cold, gasoline atomization is reduced, all causing the mixture in the combustion chambers to be leaner than desired. Choking systems associated with the carburetor to vary the air fuel mixture are well known and are often used to assist cold weather starting. It is also known to use primer devices to enrich the fuel mixture in lieu of or in combination with choking systems. Primers offer several advantages over choking, such as, by way of example, elimination of adjustment error, less cost associated with the manufacture of the engine and fewer moving parts, reducing the possibility of breakdown or malfunction. In same applications, the primer may be used to start the engine and a choking system may be used to operate the engine until running temperature is achieved, particularly in severe cold starting conditions.
Known priming devices are typically in the form of an operator actuated priming bulb which, when depressed, displaces fuel into the engine intake system. Dry primers first displace air into a fuel chamber to indirectly induce fuel into the intake of the engine. Wet primers are continuously filled with fuel and displace it directly into the intake of the engine when depressed.
The prior art devices have been of relatively complex design, see for example U.S. Pat. Nos. 4,679,534; 4,589,586; 4,197,825; 3,948,589; and U.S. Pat. No. 3,494,343. In particular, U.S. Pat. No. 4,404,933 discloses a primer device comprising a primer bulb that is fitted directly into a self-sealing base. As there shown, the primer bulb is a two-piece assembly with the bulb of resilient material including an integral annular mounting ring. The base is made of a stiff material having a channeled rim for receiving the annular ring on the primer bulb. The base is adapted to be wedged into a suitable receptacle in communication with the engine fuel system. U.S. Pat. No. 4,197,825 discloses an annular sealing member for attaching a primer bulb on the body of a float type carburetor. The bulb is maintained in an annular groove by the sealing member which is pressed against the primer bulb to provide an axial compression force on the annular flange of the bulb. U.S. Pat. No. 4,679,534 includes a channel provided in the carburetor body by an interior and exterior annular flange on the carburetor. The primer bulb is placed in the channel and is compressed axially into the channel by a retainer.